[FileCheck] Given multiple -dump-input, prefer most verbose

Problem: `FILECHECK_OPTS` was implemented so that a test runner, such
as a bot, can specify FileCheck debugging options, such as
`-dump-input=fail`.  However, some existing test suites have FileCheck
calls that already specify `-dump-input=fail` or `-dump-input=always`.
Without this patch, such tests fail under such a test runner because
FileCheck doesn't accept multiple occurrences of `-dump-input`.

Solution: This patch permits multiple occurrences of `-dump-input` by
assigning precedence to its values in the following descending order:
`help`, `always`, `fail`, and `never`.  That is, any occurrence of
`help` always obtains help, and otherwise the behavior is similar to
`-v` vs. `-vv` in that the option specifying the greatest verbosity
has precedence.

Rationale: My justification for the new behavior is as follows.  I
have not experienced use cases where, either as a test runner or as a
test author, I want to **limit** the permitted debugging verbosity
(except as a test author in FileCheck's or lit's test suites where the
FileCheck debugging output itself is under test, but the solution
there is `env FILECHECK_OPTS=`, and I imagine we should use the same
solution anywhere else this need might occur).  Of course, as either a
test runner or test author, it is useful to **increase** debugging
verbosity.

Reviewed By: probinson

Differential Revision: https://reviews.llvm.org/D70784

0 files changed, 0 insertions, 0 deletions